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Pelvic osteotomy for treatment of pelvic malunion and obstipation in dogs and cats

Arnold S. Lesser, VMD, Diplomate ACVS

Summary

Pelvic osteotomy and realignment of fracture fragments can be used to correct malunion and chronic obstipation associated with narrowing of the pelvic canal. Malunited fracture fragments are separated, aligned in their normal positions, and stabilized with plates, screws, and/or pins. Even though patients may resume walking after treatment of pelvic fracture with cage rest, callus formation and/or pelvic collapse may result in chronic obstipation. A dog and 3 cats, with chronic obstipation secondary to pelvic fractures, were successfully treated with pelvic osteotomy and fracture realignment.

Treatment of pelvic fractures in dogs and cats has been a subject of controversy for years. Though open reduction is required for intraarticular fractures and collapse of the pelvic canal, many practitioners routinely elect conservative treatment in the form of cage rest.

Depending on the nature of the fracture, conservative treatment may be adequate; however, if the pelvic ring has collapsed, conservatively treated patients that become ambulatory may later develop severe, chronic obstipation after the fractures heal in an improper position (malunion). Also, such complications may arise after inadequate open reduction or because of callus formation within the pelvic canal. Long-term use of stool softeners to facilitate fecal passage is inevitably futile.

Pelvic osteotomy, which involves separating the malunited pelvic fragements and reassembling them in their proper position, is an alternative to euthanasia in cases of pelvic fracture malunion. This report describes use of pelvic osteotomy in 4 animals with pelvic fracture malunion.

Case 1

A 2-year-old, 35-kg Siberian Husky bitch was originally treated for ilial, pubic and ischial fractures with only a single hemicerclage wire placed across the ilial fracture (Figs 1, 2). Soon after the initial surgery, the fracture fragments became misaligned and healed in a malunion (fig 3). A year after surgery, the dog was presented for treatment of obstipation.

Triple pelvic osteotomy was used to widen the pelvic canal and replace the pelvic bones in their normal positions. Pubic and ischiatic osteotomies allowed mobilization of the hemipelvis after separating the ilial fragments. The ilium was stabilized with a 6-hole decompression plate (Fig 4). The pubic osteotomy was made from a separate ventral incision. The animal recovered fully and obstipation did not recur.

Case 2

A 7-year-old, 4-kg Siamese queen, found as a stray, had a history of chronic obstipation. Radiographs revealed malunion of multiple pelvic fractures, with medial displacement of the left ilium (Fig 5).

The pelvic symphysis was osteotomized via a ventral approach, allowing lateral reduction of the ilium. A right-angle decompression plate was used to secure the ilium, and the symphysis was united with 22-ga stainless-steel wire (Fig 6). Postoperative knuckling on the left rear limb suggested sciatic nerve compression, which was corrected at a second surgery 9 days later by removing the fibrous tissue, compressing the nerve and padding the nerve with fat where it passed near the ilial fracture site. Though the pelvic canal was sufficiently widened by osteotomy, stool softener use was required indefinitely because of chronic colonic dilation.

Case 3

A 7-year-old, 3.5-kg castrated domestic shorthaired cat sustained multiple pelvic fractures and a coxofemoral luxation (Fig 7). The left femoral head and neck were excised, and the left acetabulum and right sacroiliac joint stabilized (Fig 8); however, the repair left the pelvic ring incomplete, resulting in subsequent collapse of the pelvis (Fig 9).

Chronic obstipation necessitated further surgery 20 months later, when the ilium was osteotomized, displaced laterad and plated. The ischial nonunion was wired to complete the pelvic ring (Fig 10). The cat was walking well and defecating normally a month after surgery.

Case 4

A 7-year-old, 4-kg castrated male domestic shorthaired cat sustained pelvic fractures and was treated with cage rest. Subsequent narrowing of the pelvic canal resulted in severe, chronic obstipation necessitating periodic manual rectal evacuation under general anesthesia (Fig 11).

The ilial fracture union was separated by blunt dissection and the fragments displaced laterad and plated after osteotomy of the ischium and pubis. A Steinmann pin was inserted for added support (Fig 12). The repair sufficicently widened the pelvic canal to allow normal stool passage.

Discussion

In these 3 animals, conservation treatment or inadequate surgical repair led to malunion and chronic obstipation. Pelvic osteotomy corrected the condition in all cases. The only complication involved the cat in…